The contactors of the starters according to the prior art have two functions, firstly to displace the launcher which supports the pinion by means of a fork, such as to allow the pinion to engage on the crown of the thermal engine to be started, and secondly to supply power to the electric motor of the starter, thus making it possible to rotate the pinion. For this purpose, the contactors comprise a set of coils which make it possible to displace the mobile part of a magnetic core, with the mobile part of the magnetic core giving rise both to the displacement of the fork and the displacement of a contact device comprising a contact plate which is designed to establish an electrical contact between the supply terminals of the electric motor.
In addition, springs known as the compression spring and the return spring are placed on both sides of the plate, such as to constrain the plate against the terminals when the coils are activated and displace the plate towards the terminals, and to facilitate the return of the plate to the initial position when power is no longer supplied to the coils.
However, with the systems according to the prior art, the plate may rebound once or more on the terminals when power is supplied to the coils. This rebound/these rebounds give(s) rise to poor contact and disrupt(s) the functioning of the starter.
In addition, the contact devices according to the prior art generally comprise a large number of parts, which gives rise to complex assembly.
In particular, means for assembling a rod, springs and stops are known from patent application FR2957711. For example, in this patent application, assemblies exist with stops which are fitted on the rod in order to retain a compression spring. According to one embodiment, a washer of the bayonet type is described, fitted onto the contact rod. This embodiment makes it necessary to produce a shaft with a flattened shoulder and a groove. In addition, the production method is very complicated using a machine, since it is necessary to be able to index the washer relative to the shoulder, and turn the latter whilst exerting pressure on the compression spring.
This embodiment is thus complex to implement. Other embodiments described in order to solve this problem of complex fitting, as well as a rod without a shoulder. For example, an embodiment is described in which the assembly comprises a washer with claws fitted onto the contact rod, however with an embodiment of this type, with many cycles of use, as is the case for reinforced starters (i.e. a starter which starts a thermal engine which is switched off spontaneously when the vehicle stops, for example at a red light) which require a number of cycles four times greater than with a so-called standard starter, there is a risk that the washer with claws will break or withdraw towards the fixed core, leaving a gap relative to the compression spring, and thus giving rise to malfunctioning of the starter. In fact, in a case of this type, it may happen that the compression spring is no longer functional, and therefore no longer ensures the contact between the contact plate and the terminals. According to another embodiment of this document, an embodiment is described in which a pin is added in the shaft in order to retain a washer which forms the stop of the compression spring. However, an embodiment of this type is complex to implement because of the forced insertion into the shaft of a pin which may break during the assembly. Furthermore there are two parts to be assembled instead of one in comparison with the other embodiments, thus making the assembly more complex. In addition, an assembly of this type may not allow the contact rod to be supported on the fixed core. In fact, in an embodiment of this type, in the state of rest, it is the plate which is supported on the fixed core, which can cause it to become deformed.
In addition, in all of these embodiments, as well as in the prior art, the spring for compression of the plate against the terminals can become misaligned relative to the rod, thus giving rise to an imbalance of the forces of the spring on the plate against the terminals. This results in the risk of an arc between the plate and the terminal, since the plate is inclined, and therefore comes into contact with one terminal before the other terminal. These arcs give rise to premature wear of the plate.